1. Field of the Invention
The present disclosure relates to a method of overcurrent detection voltage correction and a battery protection integrated circuit.
2. Description of the Related Art
Conventionally, a battery protection integrated circuit is known, which includes a transistor connected between a negative electrode terminal of a secondary battery and a negative electrode terminal of a battery charger and a control chip for controlling charge/discharge of the secondary battery by turning on and off the transistor (for example, see Patent Document 1).
Meanwhile, an overcurrent detection circuit is known, which monitors a magnitude relation of a voltage between a negative electrode terminal of a secondary battery and a negative electrode terminal of a load and an overcurrent detection voltage set for detecting the overcurrent of the secondary battery, thereby detecting the overcurrent (for example, see Patent Document 2). The overcurrent detection circuit detects the overcurrent by using a voltage variance in accordance with a voltage reduction due to an on-resistance of the transistor connected between the terminals.
However, a value of the on-resistance of the transistor is likely to vary due to manufacturing irregularity, temperature variance, variance of the gate voltage of the transistor, etc. Therefore, when overcurrent detection voltages of the respective battery protection circuit are set to be the same voltage value, current values (overcurrent detection value) of the detected overcurrent are varied according to the respective battery protection integrated circuits.
FIG. 1 is a diagram for illustrating an example variation of the overcurrent detection values due to the temperature variance in three samples of the battery protection integrated circuit A, B and C. The on-resistance (hereinafter, referred to as “Rsson”) of the transistor is likely to vary due to the manufacturing irregularity of the samples A, B and C, or the temperature variance. Therefore, in a case where the overcurrent detection voltages Viover of the samples A, B and C are set to be the same voltage value within a certain temperature range including a reference temperature T0, the overcurrent detection values Iover are varied according to the samples A, B and C.
FIG. 2 is a diagram for illustrating an example variation of the overcurrent detection values due to gate voltage variance in the three battery protection integrated circuit samples of A, B and C. Rsson is likely to vary due to the manufacturing irregularity of the samples A, B and C or the variance of the gate voltage VGS. Therefore, in a case where the overcurrent detection voltages Viover of the samples A, B and C are set to be the same voltage value within a certain gate voltage range including a reference gate voltage value Vgs0, the overcurrent detection values Iover are varied according to the samples A, B and C.